Multiple emergency vehicles and officers were seen on Western Avenue, which runs through the city campus, just after 9am.
A NSW Ambulance spokesperson confirmed they had been called to the site at about 8.30am.
A 22-year-old man has been taken to Royal Prince Alfred Hospital in a serious but stable condition.
Police said a 14-year-old boy had later been arrested near the hospital.
He is assisting with inquiries.
Neither person is believed to be known to the other, and police said there was no further risk to the community.
“A NSW Police operation is under way on our Camperdown campus,” a university spokesperson said.
“As a precautionary measure there may be an increased security and police presence on campus while investigations continue.
“The safety and wellbeing of our students, staff and members of the community is our priority, and we continue to work with authorities.”